Stationery articles such as folders, portfolios and pocket document binders have long been produced such as illustrated in U.S. Pat. Nos. 5,876,143; 5,059,052; 5,752,721 and 5,417,509, including paper folders such as U.S. Pat. Nos. 4,934,584 and 3,516,599. Vinyl folios and folders are illustrated in U.S. Pat. Nos. 5,873,513 and 4,629,349. More specifically, polyethylene, polypropylene and polyvinyl chloride articles are illustrated in patents U.S. Pat. Nos. 5,275,438; 5,445,417 and 5,266,140.
Today, paper materials are less likely to be used in stationery paper products having pockets because of the durability factor. They do not stand up under heavy service necessating more durable materials. Problems have developed with the use of folders made of certain thermoplastic materials which tend to pick up the ink from inserted letters or the like leaving the transferred ink on the folders in an unsightly manner, and often where the folders are transparent, causing interference with subsequent articles placed in the folders because of ink transferred thereon at an earlier date.
Polypropylene has been found to be a thermoplastic material which when made into folders does not pick up ink from the papers inserted therein; whereas polyethylene and polyvinyl chloride tend to pick up ink.
Metallic polyethylene, polypropylene and polyvinyl chloride thermoplastic films are found to produce exceptional fine finished articles when used with this process probably due to the heat transfer of the metallic particles in the thermoplastic films. These metallic thermoplastics consist of aluminum powders, giving a special sheen to the folder as for example in silver, gold, red, green, blue, purple, etc. The metallic thermoplastics are available from American Profil of Cedar, Rapids, Iowa.
Where heat sealing is used in the manufacture of stationery articles such as folders and the like, it has been found necessary to use a two-stage system for producing the folders. This two-stage involves sealing the marginal edges followed by a cutting operation to remove the waste of flash materials adjacent the sealed edge. Unfortunately, it has been found that the cutting operation, being subsequent, often leaves marginal strips adjacent to seal which are uneven and unsightly. Further, the subsequent cutting and squaring off of the edges produces sharp corners which often injured or at least cause annoyance to the individual using such articles. In particular, polypropylene is ordinarily difficult to tear.
In most instances where a heat sealed is used, the attempt is to make the seal even in length, height and width. Depending on material, it has been found that if the seal is made having serrations, there is less likelihood of leakage or opening up of the seal. To some extent this is dependent upon the type of thermoplastic material used.